WEMOS D1 Mini ESP8266 Data Logging Shield, RTC, micro-SD

The MEMOS D1 Mini compatible Data Logging Shield can save data like digital events and analog measurements, together with a precisely time and date stamp, on a micro SD card (FAT16/32). An optional CR1220 lithium battery keeps the timekeeper running for several years without external power supply.

These are the I/O lines the Data Logging Shield is using to connect to the WEMOS D1 Mini WiFi board: